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“A Q&A with the New York Times bestselling author about her new book that focuses on the critical connection between the health of our soil and the health of our planet.

Healthy soil can reverse global warming. That’s the big, new idea behind Kristin Ohlson’s fascinating book, The Soil Will Save Us: How Scientists, Famers, and Foodies Are Healing the Soil to Save the Planet, which is being published today by Rodale and is already garnering praise from critics and thinkers.

Ohlson, a journalist and New York Times bestselling author, is also a frequent contributor to Experience Life. She talked with us recently about the critical connection between the health of our soil and the health of our planet.

EL | What is the relationship between the loss of carbon in the soil and the excess carbon dioxide in the atmosphere?
Most people think that the overload of carbon dioxide in our atmosphere comes exclusively from the burning of fossil fuels, but that’s not true. People began adding CO2 to the atmosphere thousands of years ago through the ways they used the land. We tend to think that ancient people left a lighter footprint on the land than we do, but that’s not true. There were fewer of them, but their accumulated activities over thousands of years may have warmed the climate so much that we missed an ice age that would have occurred 2,000 years ago.

One way that they added CO2 to the atmosphere was by plowing. There is nothing in nature that opens up the soil to that depth with such regularity, and it exposes the carbon to oxygen so that it forms carbon dioxide.

How did that carbon get in the soil? It had been accumulating there for millions of years before mammals evolved, through a partnership between plants and the microorganisms in the soil. We can’t see them with the naked eye — and we had no idea they were there until fairly recently — but the earth beneath our feet is teeming with tiny creatures. There are an incredible six billion microorganisms per tablespoon of soil. The partnership between these microorganisms and plants have created the basis for just about all life on earth.

Here’s how it works. Plants remove carbon dioxide from the air through photosynthesis and convert it into carbon-based sugars and protein to fuel their growth. But plants only use about 60 percent of this carbon-based food themselves. The rest of it is sent down to their roots, where the microorganisms cluster like pigs at a trough. The roots ooze out a carbon meal for the microorganisms. In turn, the microorganisms leave behind mineral nutrients the plants need, which they’ve liberated from sand and rock.

That carbon cycles through the soil, as the microorganisms both eat it and use it to build tiny structures for protection and to hold water. Finally, the carbon is “fixed” in the soil, semi-permanent, until hit by a disturbance like plowing.” Read interview